Fuel pump

ABSTRACT

In a fuel pump, an impeller is rotatably accommodated between a suction side cover and a pump casing. A pump channel of the suction side cover is positioned on an axial side opposite to a fuel discharge port with respect to the impeller. The impeller has blade grooves circumferentially outside and communicating holes circumferentially inside. A wall of a terminal end portion of the pump channel of the suction side cover has a guide portion directing from the blade grooves toward the communicating holes. The terminal end portion is pointed in shape in a rotation direction of the impeller. Fuel pressurized in the pump channel is guided from the blade grooves to the communicating holes at the terminal end portion without steeply reducing flow speed and flows through the communicating holes to the fuel discharge port.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is based upon and claims the benefit of priority of Japanese Patent Applications No. 2003-137070 filed on May 15, 2003 and No. 2004-65264 filed on Mar. 9, 2004, the contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a fuel pump in which pressure of fuel sucked thereto is increased by rotating a rotary member having a plurality of blade grooves arranged in a rotation direction thereof.

BACKGROUND OF THE INVENTION

[0003] Patent documents such as EP-1286041A, JP-A-2001-342983 and JP-A-Hei08-014184 disclose fuel pumps in each of which pressure of sucked fuel is increased by rotating a rotary member having a plurality of blade grooves circumferentially formed on its outer periphery. Each of those conventional fuel pumps has a case member in which the rotary member is rotatably housed. The case member has a pump channel extending from a fuel suction port to a fuel discharge port so as to form grooves along the blade grooves so that, according to rotation of the rotary member, fuel is sucked from the fuel suction port and pressurized during a period when the fuel is fed through the pump channel and the pressurized fuel is discharged from the fuel discharge port.

[0004] In the conventional fuel pumps, the pressurized fuel is likely to hit an end wall of a terminal end portion of the pump channel formed in the case member so that flow speed of the fuel decreases. As a result, fuel pressure may fluctuate, that is, fuel pressure pulsation may occur at the terminal end portion of the pump channel. In particular, since the pressurized fuel in the pump channel on an axial side of the rotary member has to be fed axially beyond the rotary member toward the fuel discharge port positioned on an axial opposite side to the rotary member, the pressurized fuel strikes against the end wall of a terminal end portion of the pump channel formed in the case member so that the fuel pressure pulsation is likely to occur. When the fuel pressure pulsation arises in the fuel flowing in the pump channel, the fuel pump vibrates and noise may be produced from the fuel pump.

SUMMARY OF THE INVENTION

[0005] An object of the present invention is to provide a fuel pump with less noise sound.

[0006] To achieve the object, in the fuel pump having a rotary member and a case member rotatably accommodating the rotary member therein, the rotary member has a plurality of blade grooves and a plurality of communicating holes. The blade grooves are formed on one and another axial end faces of the rotary member at given intervals in a rotation direction of the rotary member, respectively. The communicating holes are arranged at circumferential positions shifted in a radial direction from the blade grooves at given intervals in the rotation direction and formed so as to pass through the rotary member from the one axial end face thereof to the another axial end face thereof. The case member has a fuel suction port, a fuel discharge port and a pump channel. The pump channel, which is provided with a start end portion communicating with the fuel suction port and with a terminal end portion communicating with the fuel discharge port, is formed to extend from the start end portion to the terminal end portion along the blade grooves in the rotation direction of the rotary member so that fuel is sucked from the fuel suction port, pressurized in the pump channel and discharged from the discharge port by a rotation of the rotary member. The fuel discharge port is formed on a side of the one axial end face of the rotary member.

[0007] With the fuel pump mentioned above, it is preferable that a channel wall forming the terminal end portion of the pump channel on a side of the another axial end face of the rotary member has a guide portion for guiding the fuel from a circumferential position facing the blade grooves toward a circumferential position facing the communicating holes.

[0008] The communicating holes may be formed at a circumferential position radially inside or outside the blade grooves so that the guide portion guides the fuel to flow radially inward or outward from the circumferential position facing the blade grooves into the circumferential position facing the communicating holes.

[0009] Further, at least a part of the guide portion includes a channel wall side face directed gradually and smoothly from the circumferential position facing the blade grooves toward the circumferential position facing the communicating holes. It is preferable that the channel wall side face is formed in an arc shape.

[0010] In addition to or instead of the guide portion mentioned above, a cross sectional area of the terminal end portion of the pump channel on a side of the another axial end face of the rotary member may be gradually smaller toward a tip end of the terminal end portion thereof in the rotation direction of the rotary member. That is, the terminal end portion is formed generally in a pointed shape by making the depth thereof shallower or making the width thereof narrower toward the tip end thereof.

[0011] With the construction mentioned above, the fuel pressurized in the pump channel on a side of the another axial end face of the rotary member is smoothly guided to the communicating holes by the guide portion of the terminal end portion and/or specialized shape of the terminal end portion whose sectional area is gradually narrowed toward the tip end thereof. Therefore, the fuel pressurized in the pump channel on a side of the another axial end face flows through the communicating holes toward the fuel discharge port positioned on an axially opposite side to the pump channel on a side of the another axial end face with respect to the rotary member without steeply reducing the fuel flow speed. Accordingly, the fuel pressure pulsations at the terminal end portion can be remarkably reduced, which results in reducing the noise sound of the fuel pump.

[0012] Furthermore, pump efficiency is remarkably increased, since the fuel flow speed is not steeply reduced at the terminal end of the pump channel. The pump efficiency is operation efficiency of the pump comprising the rotary member and the casing member and can be defined by the formula, (Q*P/T*N), where Q is discharge amount, P is discharge pressure, T is torque and N is revolution number of the pump. As a value of the formula is higher, the pump efficiency is more improved.

[0013] In a case that the guide portion is not provided and the terminal end portion is formed in a pointed shape, each of the pump channels on both sides of the one and another axial end faces is widened at the start end portion and the terminal end portion in the direction in which the communicating holes are shifted from the blade grooves so that each of the start and terminal end portions faces both of the blade grooves and the communicating holes.

[0014] In a case that the guide portion is provided, the pump channel on a side of the one axial end face of the rotary member is widened at the start end portion and the terminal end portion in the direction in which the communicating holes are shifted from the blade grooves so that each of the start and terminal end portions on a side of the one axial end face of the rotary member faces both of the blade grooves and the communicating holes, and the pump channel on a side of the another axial end face of the rotary member is widened at the start end portion in the direction in which the communicating holes are shifted from the blade grooves so that the start end portion on a side of the another axial end face of the rotary member faces both of the blade grooves and the communicating holes.

[0015] In both cases mentioned above, the pump channels on both sides of the one and another axial end faces communicate with each other through the communicating holes at each of the start and terminal end portions. Accordingly, the fuel supplied from the fuel suction port formed on a side of the another axial end face of the rotary member can be smoothly introduced to the start end portion of the pump channel formed on a side of the one axial end face thereof and, further, the fuel pressurized in the pump channel on a side of the another axial end face of the rotary member can be smoothly introduced to the terminal end portion communicating with the fuel discharge port formed on a side of the one axial end face of the rotary member.

[0016] It is preferable that, at each of the one and another axial end faces of the rotary member, the communicating holes are formed near the blade grooves with a partition wall therebetween. Preferably, at least one of the one and another axial end faces of the rotary member has communication passages which are formed on the partition wall and through which the blade grooves communicate with the communicating holes.

[0017] With this construction, the blade grooves are likely to communicate with the communicating holes beyond the partition wall or through the communication passages so that the pressures in the pump channels on both sides of the one and another axial end faces at the same rotating position are equalized. As a result, the rotary member is protected from being pressed in one axial direction due to the pressure difference between the pump channels. Thus, the sliding resistance between the rotary member and the case member is restricted from increasing.

[0018] Further, it is preferable that the blade grooves formed on the one axial end face and the blade grooves formed on the another axial end face are shifted in the rotation direction of the rotary member. Since a phase shift occurs between the pressure pulsation in the fuel pressurized in the pump channel on a sides of the one axial end faces and the pressure pulsation in the fuel pressurized in the pump chamber on a sides of the another axial end faces, the pressure pulsations are reduced by mutual cancellation of pressure pulsations when the fuels having pressure pulsations of different phases merge at the terminal end portion. As a result, the pressure pulsation of fuel discharged from the fuel discharge port is reduced.

[0019] Furthermore, it is preferable that the rotary member has an annular portion continuously surrounding an outer circumference of each of the blade grooves. In addition, preferably, the pump channels formed on both sides of the one and another axial end faces of the rotary member are independent from each other and in communication with the blade grooves formed on the one and another axial end faces of the rotary member, respectively, in another words, the blade grooves formed on the one axial end face of the rotary member are separated from the blade grooves formed on the another axial end face thereof to prevent fuel from flowing directly therebetween. In this case, since fuel in a course of pressurization comes in contact with the annular portion rotating with the blade grooves, fuel pressure can increase more effectively (with less frictional resistance) in the pump channel, compared with a case in that the fuel comes in contact with a stationary wall of the case member. Further, in this case, the rotary member is protected from being biased in one radial direction, and a sliding resistance between the rotary member and the case member is restricted from increasing. Further, the shaft of the rotary member is restricted from inclining due to the force applied in the radial direction. Thus, the sliding resistances between the shaft and the bearings are restricted from increasing. Moreover, the fuel swirls generated by the blade grooves in the respective pump channels do not come in contact with each other so that the respective fuel flows are prevented from being disturbed, which result in improving the fuel pressurizing efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings:

[0021]FIG. 1 is a vertical sectional view showing a fuel pump according to a first embodiment of the present invention;

[0022]FIG. 2A is a view showing a suction side cover viewed from an impeller side in the first embodiment, and FIG. 2B is a sectional view taken along line IIB-IIB in FIG. 2A;

[0023]FIG. 3 is a view showing a pump casing viewed from the impeller side in the first embodiment;

[0024]FIG. 4 is a schematic view showing an impeller and a pump channel in the suction side cover viewed from a pump casing side in the first embodiment;

[0025]FIG. 5 is an enlarged view showing blade grooves and communicating holes in the first embodiment;

[0026]FIG. 6 is a schematic sectional view showing the blade grooves and the pump channel near a terminal end portion in the first embodiment;

[0027]FIG. 7 is a schematic sectional view showing pressure increasing operation of the blade grooves and the pump channel in the first embodiment;

[0028]FIG. 8A is a view showing a suction side cover viewed from an impeller side in a second embodiment of the present invention, and FIG. 8B is a view taken along line VIIIB-VIIIB in FIG. 8A;

[0029]FIG. 9 is a sectional view showing a fuel pump according to a third embodiment of the present invention;

[0030]FIG. 10A is a view showing a suction side cover viewed from an impeller side in the third embodiment, and FIG. 8B is a sectional view taken along line XB-XB in FIG. 10A;

[0031]FIG. 11 is a view showing a pump casing viewed from the impeller side in the third embodiment; and

[0032]FIG. 12 is a schematic view showing an impeller and a pump channel in the suction side cover viewed from a pump casing side in the third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

[0033] A fuel pump 1 according to the first embodiment will now be described with reference to FIG. 1. The fuel pump 1 is, for example, an in-tank type pump installed in an interior of a fuel tank for a vehicle. The fuel pump 1 has a pump section 10 and a motor section 11 that is an electric motor.

[0034] The pump section 10 is composed of a suction side cover 13, a pump casing 16 and an impeller 20. The pump casing 16 and the suction side cover 13 are fixed to a lower end portion of a housing 12 in a state that the pump casing 16, at a lower inner circumferential portion of which the impeller 20 is housed, is sandwiched axially between the suction side cover 13 and the housing 12. A bearing member 35 is retained by an upper inner circumferential portion of the pump casing 16. The suction side cover 13 and the pump casing 16 constitute a case member in which the impeller 20, a rotary member, is rotatably housed.

[0035] A fuel discharge port 124 (refer to FIG. 3) is formed in the pump casing 16 positioned on a side of one axial end face of the impeller 20 in an axial direction of a shaft 34, which constitutes an axis of rotation of the impeller 20. A fuel suction port 112 is formed in the suction side cover 13 positioned on a side of the other axial end face of the impeller 20 in the axial direction of the shaft 34. The suction side cover 13 and the pump casing 16 are provided with generally C-shaped pump channels 110 and 120 (refer to FIGS. 2A and 3), respectively, each of which extends independently from the fuel suction port 112 toward the fuel discharge port 124 in the rotation direction of the impeller 20 and along the blade grooves 23 so as to communicate with the blade grooves 23 formed on each of the axially opposite end faces of the impeller 20. A slight clearance is provided between the lower inner circumferential portion of the pump casing 16 and an outer circumference of the impeller 20. The slight clearance, which is a gap necessary for smoothly sliding the impeller 20 in the pump casing 16, does not serve substantially as a pump channel. The pump channel 110 and the pump channel 120 constitute a pump channel 100.

[0036] The pump channel 110 is formed on a side of the other end face of the impeller 20 in an axial direction thereof, that is, on a side axially opposite to the fuel discharge port 124 with respect to the impeller 20. As shown in FIGS. 2A and 4, the pump channel 110 formed in the suction side cover 13 has a start end portion 113 communicating with the fuel suction port 112. The most inner circumferential position of the start end portion 113 coincides substantially with the most inner circumferential position of each of communicating holes 24 of the impeller 20, as shown in FIG. 4. The most outer circumferential position of the start end portion 113 coincides substantially with the most outer circumferential position of each of the blade grooves 23 of the impeller 20 as shown in FIG. 4. The start end portion 113 has a sufficient length in a radial direction of the impeller 20 so as to directly face at least one of the blade grooves 23 and at least one of the communicating holes 24. That is, the start end portion 113 is widened radially so as to communicate simultaneously with both of limited numbers of the blade grooves 23 and the communicating holes 24.

[0037] The pump channel 110 also has a terminal end portion 116. An air evacuation hole 114 is formed in the pump channel 110 between the start and terminal end portions 113 and 116. The position of the terminal end portion 116 is gradually shifted inward in a radial direction of the impeller 20 from the position where the terminal end portion 116 communicates only with the blade grooves 23 to the position where the terminal end portion 116 communicates only with the communicating holes 24 located radially inside the blade grooves 23. The terminal end portion 116 is formed in a pointed shape so that a cross sectional area of the terminal end portion 116 is gradually smaller in the rotation direction of the impeller 20.

[0038] The pump channel 110 is a side groove 14 formed in the suction side cover 13. The side groove 14 is provided at an entrance of the terminal end portion 116 with a guide portion 15 extending inward in a radial direction of the impeller 20 from the circumferential position facing only the blade grooves 23 toward the circumferential position facing only the communicating holes 24. An outer circumferential side groove wall (a channel wall side face) 15 a of the guide portion 15 is formed in an arc shape. An inner circumferential position of a leading end of the terminal end portion 116 coincides with the most inner circumferential position of each of the communicating holes 24. An outer circumferential side groove wall 15 b at the leading end of the terminal end portion 116 is formed also in shape of an arc which extends radially inward more gently, compared with the arc shape of the outer circumferential side groove wall 15 a.

[0039] Dot-dash lines 200 and 202 in FIG. 2A show outer and inner circumferential positions of the communicating holes 24 of the impeller 20. As shown in FIGS. 2A and 2B, a groove depth of the terminal end portion 116 in the axial direction of the suction side cover 13 is made shallower with a tapered bottom and a groove radial width thereof is made narrower in the rotation direction of the impeller 20. That is, a cross sectional area of the terminal end portion 116 is smaller toward the leading end (tip end) thereof in the rotation direction of the impeller 20.

[0040] As shown in FIG. 3, the pump channel 120 formed in the pump casing 16 has a start end portion 122 whose radial width, length in a radial direction of the impeller 20, is substantially same as that of the start end portion 113 of the pump channel 110 formed in the suction side cover 13. The most inner and outer circumferential positions of the start end portion 122 coincide with the most inner circumferential position of each of the communicating holes 24 and the most outer circumferential position of each of the blade grooves 24, respectively, so that the start end portion 122 directly faces both of at least one of the blade grooves 23 and at least one of the communicating holes 24, that is, the start end portion 122 is radially widened to communicate simultaneously with both of limited numbers of the blade grooves 23 and the communicating holes 24.

[0041] The pump channel 120 has a terminal end portion 123 communicating with the fuel discharge port 124. The most inner circumferential position of the terminal end portion 123 coincides substantially with the most inner circumferential position of each of the communicating holes 24 of the impeller 20 and the most outer circumferential position of the terminal end portion 123 coincides substantially with the most outer circumferential position of each of the blade grooves 23 of the impeller 20. The terminal end portion 123 has a sufficient length in a radial direction of the impeller 20 so as to directly face at least one of the blade grooves 23 and at least one of the communicating holes 24 so that the terminal end portion 123 may communicate simultaneously with both of limited numbers of the blade grooves 23 and the communicating holes 24.

[0042] As shown in FIGS. 4 and 5, the impeller 20, which is formed in shape of a disk plate, is provided at each of outer circumferential peripheries of the one and the other side faces thereof (opposite side faces of the impeller in the axial direction of the shaft 34) with blades 22 and the blade grooves 23 alternately arranged in a rotation direction thereof. FIG. 4 shows only a part (about a half) of the blades 22 and the blade grooves 23 which are circularly arranged in the rotation direction of the impeller 20. A dot-dash line 204 in FIG. 4 shows an outermost circumferential periphery of the impeller 20.

[0043] The blade grooves 23 circumferentially adjacent are partitioned with each of the blades 22. As shown in FIG. 6, the blade grooves 23 on the one and the other axial side faces of the impeller 20 are shifted (zigzagged) from each other by half of the groove forming pitch in the circumferential direction. The blade grooves 23 on the one axial end face of the impeller 20 are isolated from the blade grooves 23 on the other axial end face of the impeller 20 so that fuel does not flow directly between the blade grooves 23 on the one and the other axial end faces of the impeller 20.

[0044] Though parts of the blade grooves 23 on the one and the other axial end faces of the impeller 20 overlap in FIG. 7, each of the blade grooves 23 on the one axial end face does not communicate with each of the blade grooves 23 on the other axial end face, since the blade grooves 23 on the one and the other axial end faces of the impeller 20 are shifted from each other by half of the groove forming pitch in the circumferential direction. A cross sectional view shown in FIG. 6 does not show axial tip end portions (innermost portions) of the blade grooves 23 of the one and the other axial end faces of the impeller 20. Each of the axial tip end portions of the blade grooves 23 of the one and the other axial end faces of the impeller 20 extends up to a position beyond an axially intermediate portion of the impeller 20.

[0045] As shown in FIGS. 4 and 5, an annular portion 21 is positioned radially outside the blade grooves 23 so as to surround the blades 22 and the blade grooves 23. The communicating holes 24 extend through the impeller 20 in an axial direction thereof. The communicating holes 24 are formed at positions beyond and adjacent partitions 25 radially inside the blades 22 and the blade grooves 23. The number of the communicating holes 24 is equal to the number of the blade grooves 23. Communicating passages 26, through each of which each of the blade grooves 23 and each of the communicating holes 24, are formed on the partitions 25 on opposite axial end faces of the impeller 10. Each of the communicating passage 26 allows to make each of the blade grooves 23 b, 23 c, 23 d formed on one axial end faces of the impeller 20 communicate with each of the blade grooves 23 b, 23 c, 23 d formed on the other axial end faces of the impeller 20, which is circumferentially shifted from each of the blade grooves 23 b, 23 c, 23 d formed on the one axial end faces of the impeller 20 by half of the groove forming pitch, as shown in FIG. 6.

[0046] As shown in FIG. 1, the motor section 11 is composed of the housing 12, permanent magnets 30, an armature 40 and a commutator 70. The housing 12 is made of magnetic material. The suction side cover 13 and a discharge side cover 18 are fixed to the housing 12 by crimping or staking opposite axial ends of the housing 12. Four permanent magnets 30, each of which is formed in shape of a one-fourth arc, are mounted circumferentially on and fixed by resin material 32 to inner circumferential wall of the housing 12. The four permanent magnets 30 form four magnetic poles whose polarities are different in a rotation direction of the shaft 34.

[0047] The armature 40 has the commutator 70 on one of axial ends thereof. The shaft 34, which is a rotation axis of the armature 40, is held by bearing members 35 and 36 which are housed in and held by the pump casing 16 and the discharge side cover 18, respectively. The armature 40 has six magnetically polarized coil sections 50 arranged in a rotation direction thereof. Each of the six coil sections 50 has the substantially same construction and has a core 52, a bobbin 60 and a coil 62 wound on the bobbin 60. Each end of the coils 62 on a side of the commutator 70 is connected in circuit with each of terminals 64 and each end of the coils 62 on a side opposite to the commutator 70 is connected in circuit with each of terminals 65. The terminals 65 are connected in circuit with a terminal 66.

[0048] The commutator 70 has six segments 72 arranged in a rotation direction thereof. The segments 72 are electrically insulated one another by a gap formed between two adjacent segments 72 and insulating resin material 73. A terminal 74 can be connected in circuit with each of the segments 72 and with the terminals 64 on a side of the commutator 70.

[0049] An operation of the fuel pump 1 is described herein after.

[0050] When the impeller 20 rotates with the armature 40, vacuum arises in the fuel suction port 112. As a result, fuel is sucked from the fuel suction port 112 into the start end portion 113 of the pump channel 110. The start end portion 113 of the pump channel 110 and the start end portion 122 of the pump channel 120 directly face to and communicate with the blade grooves 23 and the communicating holes 24, respectively. The fuel sucked from the fuel suction port 112 into the start end portion 113 not only flows into the blade grooves 23 on a side of the pump channel 110 but also flows into the blade grooves 23 on a side of the pump channel 120 from the start end portion 113 through the communicating holes 24 and the start end portion 122. Then, as shown in FIG. 7, a swirl generated in one of the blade grooves 23 by the rotation of the impeller 20 flows into the subsequent blade groove 23 existing rearward relative to the rotation direction of the impeller 20. By repeating this operation among a multiple of the blade grooves 23 provided in the rotation direction, circular flows are generated in the blade grooves 23 and the pump channel 110 and in the blade grooves 23 and the pump channel 120, respectively. Thus, the respective fuel in the pump channels 110 and 120 are independently pressurized while flowing from the fuel suction port 110 toward the fuel discharge port 124.

[0051] As shown in FIG. 6, at the terminal end portions 116 and 123 of the pump channels 110 and 120, communication between the blade grooves 23 and the terminal end portion 116 of the suction side cover 13 is closed earlier than communication between the blade groove 23 and the terminal end portion 123. As the blade grooves 23 on a side of the terminal end portion 123 are closed one by one, the fuel flowing through the blade grooves 23 and the pump channel 110 is guided toward the communicating holes 24 positioned radially inside the glade grooves 23 by the outer circumferential side groove wall 15 a of the terminal end portion 116. Since the outer circumferential side groove wall 15 a is in a smooth arc shape, the fuel pressurized in the pump channel 110 is guided radially inward from a position facing the blade grooves 23 to a position facing the communicating holes 24 without substantial flow speed decrease.

[0052] The fuel guided from the position of the blade grooves 23 to the position of the communicating holes 24 flows toward the terminal end portion 123 of the pump channel 120 through the communicating holes 24 at the terminal end portion 116 of the pump channel 110. The fuel in the pump channels 110 and the fuel in the pump channel 120 merge at the terminal end portion 123. The blade grooves 23 formed on the one and the opposite axial end faces of the impeller 20 are shifted in position by half of the groove forming pitch in the rotation direction thereof. Therefore, a phase shift occurs between the pressure pulsation in the fuel pressurized in the pump channel 110 and the pressure pulsation in the fuel pressurized in the pump chamber 120. When the fuels having pressure pulsations of different phases thus merge at the terminal end portion 123, the pressure pulsations are reduced by mutual cancellation of pressure pulsations. As a result, the pressure pulsation of fuel discharged from the fuel discharge port 124 is reduced.

[0053] The fuel discharged from the fuel discharge port 124 is directed to flow toward the commutator 70 through the outer periphery of the armature 40 and discharged from the fuel pump 1 to an engine through a fuel outlet port 130.

[0054] Since the pressures of fuels pressurized in the pump channels 110 and 120 respectively increase with rotation of the impeller 20 from the fuel suction port 112 to the fuel discharge port 124. The fuel pressures in the pump channels 110 and 120 have pressure gradients in a rotation direction of the impeller 20. The fuel pressures in the blade grooves 23 also increase in the rotation direction from the fuel suction port 112 to the fuel discharge port 124.

[0055] Here, the pump channel 110 and the pump channel 120 are formed on both sides of the rotation axis of the impeller 20 independently from each other and do not directly communicate with each other, and no pump channel is formed at the outer circumference of the impeller 20. In addition, the annular portion 21 surrounding the outer circumferential portion of the blade grooves 23 rotates with the blade grooves 23. Therefore, since the fuel pressures in the pump channels 110 and 120 as well as the fuel pressures in the blade grooves 23 are different in a rotation direction of the impeller, the impeller 20 is protected from receiving a force in one radial direction. Thus, the impeller 20 is protected from being biased in one radial direction, and a sliding resistance between the impeller 20 and the inner circumferential wall of the pump casing 16 is restricted from increasing.

[0056] Since the impeller 20 does not receive a force in one radial direction due to pressure difference in the rotation direction, the shaft 34 is restricted from inclining due to the force applied in the radial direction. Thus, the sliding resistances between the shaft 34 and the bearings 35 and 36 are restricted from increasing.

[0057] When the fuels are pressurized in the pump channels 110 and 120 respectively, a difference in pressures may arise at the same rotating position between the pump channel 110 and the pump channel 120. Since the pump channels 110 and 120 are formed independently on both sides of the rotation axis and the pump channels 110 and 120 which are in the middle of pressurization communicate with only the blade grooves 23 to which each of the pump channels 110 and 120 faces, the pump channel 110 and the pump channel 120 do not communicate with each other. Therefore, the difference between fuel pressures in the pump channel 110 and the pump channel 120 at the same rotating position cannot be canceled out.

[0058] However, the communication passages 26 are formed on both axial side end faces of the impeller 20 in the partition wall 25 separating the blade grooves 23 and the communicating holes 24. As a result, the blade grooves 23 located on both sides in the axial direction of the shaft 34 communicate with each other by the communication passages 26 and the communicating holes 24. Further, the communicating holes 24 are formed near the inner circumferential side of the blade grooves 23 while being separated by the thin partition wall 25. Accordingly the communication distance between the blade grooves 23 and the communicating holes 24 is shortened in the course of pressurization. As a result, the difference in the pressures in the pump channel 110 and the pump channel 120 at the same rotating position can be readily canceled.

[0059] Since the pump channels 110 and 120 communicate indirectly with each other by the blade grooves 23, the communication passages 26 and the communicating holes 24 to which each pump channel faces, the pressures in the pump channel 110 and the pump channel 120 at the same rotating position are equalized. As a result, the impeller 20 is protected from being pressed in one axial rotation direction due to the pressure difference between the pump channel 110 and the pump channel 120 at the same rotating position. Thus, the sliding resistance between the impeller 20 and the suction side cover 13 or the pump casing 16 is restricted from increasing.

[0060] In addition, the guide portion 15 guides fuel from the blade grooves 23 to the communicating holes 24, which is on the inner circumferential side, at the terminal end portion 116 of the pump channel 110. The outer circumferential side groove wall 15 a of the guide portion 15 is formed in an arc shape. As a result, the fuel guided from the blade grooves 23 to the communicating holes 24 on the inner circumferential side is restricted from decreasing its flow speed. Still further, the terminal end portion 116 is formed in a pointed shape in the rotation direction and the space of the terminal end portion 116 is gradually narrowed. Therefore, the fuel is restricted from striking against the side groove face 14 at the terminal end portion 116 and losing flow speed. Thus, the fuel pressure pulsation at the terminal end portion 116 of the pump channel 110 can be reduced and noise sound generated in the pump section 10 can be reduced.

[0061] Additionally, the blade grooves 23 formed on both axial end faces of the impeller 20 in the axial direction of the shaft 34 are separated from each other and the fuels therein do not directly contact. Therefore, the fuel swirls generated by the blade grooves 23 are prevented from being disturbed and the fuel pressurizing efficiency is improved.

Second Embodiment

[0062] The second embodiment of the present invention is shown in FIG. 8, in which substantially the same structural parts as the first embodiment are designated with the same reference numerals.

[0063] The terminal end portion 142 of the pump channel 140 formed in the suction side cover 80 is shaped to be pointed in the rotation direction. That is, the depth of the terminal end portion 142 is gradually narrowed in the rotation direction, while the width of the same is substantially unchanged.

[0064] Further, the channel wall 82 of the suction side cover 80 defining the pump channel 140 has a guide portion 83 for guiding the pump channel 140 radially inward at the terminal end portion 142. The outer circumferential side wall 83 a of the guide 83 is in a smooth arc shape. Therefore, fuel is restricted from striking against the guide portion 83 at the terminal end portion 142 and from quickly losing fuel flow speed. Thus, the fuel pressure pulsation at the terminal end portion of the pump channel 140 can be reduced and the noise sound generated in the pump section 10 can be reduced.

[0065] In the first and the second embodiments, the guide portion guides fuel from the position facing the blade grooves 23 to the position facing the communicating holes 24 on the inner circumferential side at the terminal end portion of the other pump channel. Further, the terminal end portion of the other pump channel is also formed in the pointed shape. Therefore, the fuel flow speed loss at the terminal end portion of the other pump channel can be reduced. Thus, the fuel pressure pulsation at the terminal end portion 116 of the pump channel 110 can be reduced, and the noise sound generated in the pump section 10 can be reduced.

[0066] In addition, the pump efficiency can be improved because the fuel flow speed loss at the terminal end portion of the other pump channel can be reduced.

Third Embodiment

[0067] The third embodiment is shown in FIGS. 9 to 12. FIG. 9 is a sectional view taken at the same sectional position as FIG. 1. The substantially same structural parts as the first embodiment are designated with the same reference numerals.

[0068] As shown in FIG. 9, a pressure regulating valve 310 is disposed in a discharge side cover 302 of a fuel pump 300 to regulate a fuel pressure in the fuel pump 300. The pressure regulating valve 310 includes a ball 311, a spring 312 biasing the ball 311 in one direction and a valve seat 313 on which the ball 311 seats. When the pressure in the fuel pump 300 exceeds a predetermined pressure, the ball 311 leaves from the valve seat 311 against the biasing force of the spring 312 thereby to lower the pressure in the fuel pump 300.

[0069] A terminal 65 connected to the end of the coil 62 on an opposite side to the commutator 70 is electrically connected by a disk-shaped metal cover 68.

[0070] A suction side cover 320, a pump casing 324 and an impeller 330 form a pump section. The pump casing 324 is sandwiched between the suction side cover 320 and the housing 12. The suction side cover 320 and the pump casing 324 form a casing member for accommodating the impeller 330 as a rotary member.

[0071] A fuel discharge port 364 (refer to FIG. 11) is formed in the pump casing 324 positioned on a side of one axial end face of the impeller 330 in an axial direction of the shaft 34, which constitutes an axis of rotation of the impeller 330. A fuel suction port 352 (refer to FIG. 10A) is formed in the suction side cover 320 positioned on a side of the other axial end face of the impeller 330 in the axial direction of the shaft 34. The suction side cover 320 and the pump casing 324 are provided with generally C-shaped pump channels 350 and 360 (refer to FIGS. 10A and 11), respectively. Each pump channel extends independently from the fuel suction port 352 toward the fuel discharge port 364 in the rotation direction of the impeller 330 and along the blade grooves 332 so as to communicate with the blade grooves 332 formed on each of the opposite axial end faces of the impeller 330. As light clearance is provided between the lower inner circumferential portion of the pump casing 324 and an outer circumference of the impeller 330. The slight clearance, which is a gap necessary for smoothly sliding the impeller 330 in the pump casing 324, does not serve substantially as a pump channel. The pump channel 350 and the pump channel 360 constitute a pump channel 340.

[0072] The pump channel 350 is formed on a side of the other axial end face of the impeller 330 in the axial direction thereof, that is, on an axial side opposite to the fuel discharge port 364 with respect to the impeller 330. As shown in FIG. 10A, the pump channel 350 formed in the suction side cover 320 has a start end portion 353 communicating with the fuel suction port 352. The most outer circumferential position of the start end portion 353 coincides substantially with the most outer circumferential position of each of communicating holes 334 of the impeller 330. The most inner circumferential position of the start end portion 353 coincides substantially with the most inner circumferential position of each of the blade grooves 332 of the impeller 330. The start end portion 353 has a sufficient length in a radial direction of the impeller 330 so as to directly face at least one of the blade grooves 332 and at least one of the communicating holes 334. That is, the start end portion 353 communicates simultaneously with both of limited numbers of the blade grooves 332 and the communicating holes 334.

[0073] The pump channel 350 also has a terminal end portion 354. The position of the terminal end portion 354 is gradually shifted outward in a radial direction of the impeller 330 from the position where the terminal end portion 354 communicates only with the blade grooves 332 to the position where the terminal end portion 354 communicates only with the communicating holes 334 located radially outside the blade grooves 332. The terminal end portion 354 is formed in the pointed shape so that the space volume of the terminal end portion 354 is smaller in the rotation direction of the impeller 330.

[0074] The pump channel 350 is defined by a side groove wall (channel wall) 322 formed in the suction side cover 320. The side groove wall 322 is provided at an entrance of the terminal end portion 354 with a guide portion 356 extending outward in a radial direction of the impeller 330 from the position facing only the blade grooves 332 toward the position facing only the communicating holes 334. An inner circumferential side groove wall 356 a of the guide portion 356 is formed in an arc shape. An outer circumferential position of a leading end of the terminal end portion 354 coincides with the most outer circumferential position of each of the communicating holes 334.

[0075] A dot-dash line 400 in FIG. 10A shows the inner circumferential side position of the blade grooves 332 of the impeller 330 and dot-dash lines 402 and 404 show the outer circumferential side position and the inner circumferential side position of the communicating holes 334 of the impeller 330, respectively. As shown in FIGS. 10A and 10B, a groove depth of the terminal end portion 354 is shallower and a groove radial width thereof is narrower in the rotation direction of the impeller 330.

[0076] As shown in FIG. 11, the pump channel 360 formed in the pump casing 324 has a start end portion 362 whose radial width, that is, length in a radial direction of the impeller 330, is substantially same as that of the start end portion 353 of the pump channel 350 formed in the suction side cover 320. The most outer and inner circumferential positions of the start end portion 362 coincide with the most outer circumferential position of each of the communicating holes 334 and the most inner circumferential position of each of the blade grooves 332, respectively, so that the start end portion 362 directly faces both of at least one of the blade grooves 332 and at least one of the communicating holes 334.

[0077] As shown in FIG. 12, a plurality of communicating holes 334 is provided along the outer circumferential portion of the disk-shaped impeller 330 in the rotation direction. The communicating holes 334 are formed on the inner circumferential side of (radially inside) an annular portion 338 formed on the outer circumferential edge of the impeller 330. The communicating holes 334 pass through the impeller 330 in the axial direction of the impeller 330. The blade grooves 332 are formed alternately in the rotation direction of the shaft 34 on both axial end faces of the impeller 330 at the positions shifted inward in the radial direction from the communicating hole 334. The blade grooves 332 on one side of the rotation axis are shifted by half a pitch in the rotation direction from those on the other side of the rotation axis.

[0078] Further, the blade grooves 332 on both axial end faces are separated from each other so that fuel do not directly flow therethrough. The blade grooves 332 adjacent each other in the rotation direction are partitioned from each other. The blade grooves 332 and the communicating holes 334 communicate with each other through communication passages 336 formed in the partition wall 335. The partition wall 335 continuously surrounds the outer circumference of the blade grooves 332 in the rotation direction as an annular portion.

[0079] Next, an operation of the fuel pump 300 is described.

[0080] At the terminal end portions 354 and 363 of the pump channels 350 and 360, the communication between the blade groove 332 and the terminal end portion 354 of the suction side cover 320 is closed earlier than the communication between the blade groove 332 and the terminal end portion 363. As the blade grooves 332 on the terminal end portion 23 are closed one by one, the fuel in the pump channel 350 is guided from the position facing the blade grooves 332 toward the position facing the communicating hole 334 on the outer circumferential side by the inner circumferential side groove wall 356 a of the terminal end portion 354. Since the inner circumferential side wall 356 a is in a smooth arc shape, the fuel pressurized in the pump channel 350 is guided from the position facing the blade grooves 332 to the position facing the communicating holes 334 on the outer circumferential side without substantial flow speed decrease.

[0081] The fuel guided from the position facing the blade grooves 332 to the position facing the communicating holes 334 flows toward the terminal end portion 363 of the pump channel 360 through the communicating hole 334 from the terminal end portion 354 of the pump channel 350. The fuel in the pump channels 350 and the fuel in the pump channel 360 merge at the terminal end portion 363 and are discharged from the fuel discharge port 364.

Other Emobodiments

[0082] In the first and the second embodiments, the positions of the blade grooves 23 on both sides in the rotation axis direction are shifted from each other in the rotation direction. The blade grooves 23 on both sides may be provided at the same positions in the rotation direction. It is also possible to provide a space for making the blade grooves 23 on both sides in the rotation axis direction communicate with each other between the blade grooves 23 and the annular portion 21 surrounding the outer circumference of the blade grooves 23. Further, the annular portion 21 may be eliminated.

[0083] In the second embodiment, the terminal end portion 142 on a side of the other axial end face is formed in a pointed shape by reducing the depth of the terminal end portion 142 in the direction of rotation without changing the channel width. The terminal end portion of the pump channel on a side of the other axial end face may be formed in a pointed shape by narrowing the pump channel width, while maintaining the depth of the pump channel at the terminal end portion substantially uniform.

[0084] In the first to third embodiments, the terminal end portion of the pump channel on a side of the other axial end face may be closed while maintaining the same channel area without forming in the pointed shape, as far as the pump channel on a side of the other axial end face is guided by the guide portion directing from the position facing the blade grooves to the position facing the communicating holes, which are radially shifted in the radial direction relative to the blade grooves. Further, the terminal end portion of the pump channel on a side of the other axial end face may be closed at a position facing both of the communicating hole 24 and the blade groove 23 without being directed from the position facing the blade groove 23 toward the position facing the communicating holes 24, as far as the terminal end portion of the pump channel on a side of the other axial end face is widened radially but formed in the pointed shape.

[0085] In the first to third embodiments, the fuel suction port is formed on an opposite sides to the fuel discharge port with respect to the impeller in the rotation axis direction. The fuel suction port and the fuel discharge port may be formed only on one of the axial sides of the impeller in the rotation axis direction.

[0086] In addition, in the first to third embodiments, the pump channels are formed independently of each other on both axial end sides of the impeller in the rotation axis direction and no pump channel is formed in the outer circumference side of the impeller in the radial direction. The pump channels may be formed radially outside the impeller as proposed in JP-A-2001-342983.

[0087] In the embodiments, the same number of blade grooves and the communicating holes are formed on either radially inside or radially outside of the blade grooves of the impeller. The number of communicating holes formed in the impeller may be different from the number of blade grooves. A part of the blade grooves may not communicate with the communicating holes through the communication passages, in case that the number of the communicating holes is smaller than the blade grooves and the rotational angular interval is the same as the above embodiments. It is also possible to enlarge the rotational angular interval of the communicating holes than in the above embodiments so that either one of the communicating holes corresponds to each blade groove and the blade grooves and the communicating holes communicate with each other, in the case that the number of the communicating holes is smaller than that of the blade grooves.

[0088] In the embodiments, the case member is formed by the suction port side cover and the pump casing. The case member, however, may be formed by a single member. 

1. A fuel pump comprising: a rotary member having a plurality of blade grooves and a plurality of communicating holes, the blade grooves being formed on one and another axial end faces of the rotary member at given intervals in a rotation direction of the rotary member, respectively, and the communicating holes being arranged at a circumferential position shifted in a radial direction from the blade grooves at given intervals in the rotation direction and formed so as to pass through the rotary member from the one axial end face thereof to the another axial end face thereof; and a case member rotatably accommodating the rotary member therein and having a fuel suction port, a fuel discharge port and a pump channel, the pump channel being provided with a start end portion communicating with the fuel suction port and with a terminal end portion communicating with the fuel discharge port and extending from the start end portion to the terminal end portion along the blade grooves in the rotation direction of the rotary member so that fuel is sucked from the fuel suction port, pressurized in the pump channel and discharged from the discharge port by a rotation of the rotary member, wherein the fuel discharge port is formed on a side of the one axial end face of the rotary member, and a channel wall forming the terminal end portion of the pump channel on a side of the another axial end face of the rotary member has a guide portion for guiding the fuel from a circumferential position facing the blade grooves toward a circumferential position facing the communicating holes.
 2. The fuel pump according to claim 1, wherein, the blade grooves are formed in a vicinity of an outer 5 circumference of the rotary member, the communicating holes are formed at a circumferential position radially inside the blade grooves, and the guide portion guides the fuel to flow radially inward from the circumferential position facing the blade grooves into the circumferential position facing the communicating holes.
 3. The fuel pump according to claim 1, wherein, the communicating holes are formed in a vicinity of an outer circumference of the rotary member, the blade grooves are formed at a circumferential position radially inside the communicating holes, and the guide portion guides the fuel to flow radially outward from the circumferential position facing the blade grooves into the circumferential position facing the communicating holes.
 4. The fuel pump according to claim 1, wherein at least a part of the guide portion includes a channel wall side face directed gradually and smoothly from the circumferential position facing the blade grooves toward the circumferential position facing the communicating holes.
 5. The fuel pump according to claim 4, wherein the channel wall side face is formed in an arc shape.
 6. The fuel pump according to claim 1, wherein a cross sectional area of the terminal end portion of the pump channel on a side of the another axial end face of the rotary member is gradually smaller toward a tip end of the terminal end portion thereof in the rotation direction of the rotary member.
 7. A fuel pump comprising: a rotary member having a plurality of blade grooves and a plurality of communicating holes, the blade grooves being formed on one and another axial end faces of the rotary member at given intervals in a rotation direction of the rotary member, respectively, and the communicating holes being arranged at a circumferential position shifted in a radial direction from the blade grooves at given intervals in the rotation direction and formed so as to pass through the rotary member from the one axial end face thereof to the another axial end face thereof; and a case member rotatably accommodating the rotary member therein and having a fuel suction port, a fuel discharge port and a pump channel, the pump channel being provided with a start end portion communicating with the fuel suction port and with a terminal end portion communicating with the fuel discharge port and extending from the start end portion to the terminal end portion along the blade grooves in the rotation direction of the rotary member so that fuel is sucked from the fuel suction port, pressurized in the pump channel and discharged from the discharge port by a rotation of the rotary member. wherein the fuel discharge port is formed on a side of the one axial end face of the rotary member, and a cross sectional area of the terminal end portion of the pump channel on a side of the another axial end face of the rotary member is smaller toward a tip end of the terminal end portion thereof in the rotation direction of the rotary member,
 8. The fuel pump according to claim 7, wherein, the blade grooves are formed in a vicinity of an outer circumference of the rotary member, and the communicating holes are formed at a circumferential position radially inside the blade grooves.
 9. The fuel pump according to claim 7, wherein, the communicating holes are formed in a vicinity of an outer circumference of the rotary member, and the blade grooves are formed at a circumferential position radially inside the communicating holes.
 10. The fuel pump according to claim 7, wherein each of the pump channels on both sides of the one and another axial end faces is widened at the start end portion and the terminal end portion in the direction in which the communicating holes are shifted from the blade grooves so that each of the start and terminal end portions faces both of the blade grooves and the communicating holes.
 11. The fuel pump according to claim 1, wherein, the pump channel on a side of the one axial end face of the rotary member is widened at the start end portion and the terminal end portion in the direction in which the communicating holes are shifted from the blade grooves so that each of the start and terminal end portions on a side of the one axial end face of the rotary member faces both of the blade grooves and the communicating holes, and the pump channel on a side of the another axial end face of the rotary member is widened at the start end portion in the direction in which the communicating holes are shifted from the blade grooves so that the start end portion on a side of the another axial end face of the rotary member faces both of the blade grooves and the communicating holes.
 12. The fuel pump according to claim 10, wherein the fuel suction port is formed on a side of the another axial end face of the rotary member.
 13. The fuel pump according to claim 1, wherein, at each of the one and another axial end faces of the rotary member, the communicating holes are formed in correspondence with the blade grooves.
 14. The fuel pump according to claim 1, wherein, at each of the one and another axial end faces of the rotary member, the communicating holes are formed near the blade grooves with a partition wall therebetween.
 15. The fuel pump according to claim 1, wherein, at each of the one and another axial end faces of the rotary member, the communicating holes and the blade grooves are equal in number, and at least one of the one and another axial end faces has communication passages through which the blade grooves communicate with the communicating holes.
 16. The fuel pump according to claim 1, wherein at least one of the one and another axial end faces of the rotary member has communication passages through which the blade grooves communicate with the communicating holes.
 17. The fuel pump according to claim 1, wherein the blade grooves formed on the one axial end face and the blade grooves formed on the another axial end face are shifted in the rotation direction of the rotary member.
 18. The fuel pump according to claim 1, wherein the rotary member has an annular portion continuously surrounding an outer circumference of each of the blade grooves.
 19. The fuel pump according to claim 7, wherein the rotary member has an annular portion continuously surrounding an outer circumference of each of the blade grooves.
 20. fuel pump according to claim 18, wherein the pump channels formed on both sides of the one and another axial end faces of the rotary member are independent from each other and in communication with the blade grooves formed on the one and another axial end faces of the rotary member, respectively.
 21. fuel pump according to claim 1, wherein the blade grooves formed on the one axial end face of the rotary member are separated from the blade grooves formed on the another axial end face thereof to prevent fuel from flowing directly therebetween. 